Basic programming, Step 3: configuring the throttle, Set the start voltage – SoundTraxx Tsunami Steam Users Guide User Manual
Page 20: Set the acceleration and braking rates

Tsunami Steam Sound User’s Guide
Page 17
Step 3: Configuring the Throttle
There are seven CVs that characterize the Tsunami’s throttle response and
28 more used to create a custom speed table:
CV 2, VStart
CV 3, Acceleration Rate
CV 4, Braking Rate
CV 25, Speed Table Select
CV 29, Configuration Data
CV 66, Forward Trim
CV 95, Reverse Trim
CV 67-94, Loadable Speed Table
This may sound like a lot of CVs but don’t worry; it’s not necessary to change
all of them if you don’t want to. We’ve already talked about speed step
selection in CV 29 (Step 2).
Set the Start Voltage
Tsunami provides CV 2, Vstart, to set the starting voltage that is applied to
the motor at Speed Step 1 and is used to compensate for inefficiencies in
the locomotive’s motor and driveline. CV 2 may be programmed with any
value between 0 and 255 with each step in value being about 0.5% of the
maximum available motor voltage. To calculate the value of CV 2, you can
use the formula:
Desired Starting Voltage
CV 2 = 255 X ——————————————
Maximum Motor Voltage
If your DCC system supports Operations Mode Programming, an alternative
method for setting Vstart is to turn your throttle to the first speed step and
then use the operations mode programming feature to increase the value in
CV 2 until the locomotive just begins to move.
Set the Acceleration and Braking Rates
Tsunami provides two CVs to simulate the momentum due to train weight.
CV 3, Acceleration Rate, controls how fast the locomotive responds to
increases in throttle settings and CV 4, Braking Rate, controls how fast the
locomotive will respond to decreases in the throttle setting.
Both CVs can be programmed with any value between 0 and 255 with 255
corresponding to the slowest acceleration or braking rate. Lower settings
yield a more responsive locomotive, which is useful for switching. When both
CVs are set to 0, the locomotive will respond nearly instantly to any throttle
changes. A setting of 255, on the other hand, will require several minutes for
a locomotive to reach full speed from a standing stop!
Tsunami’s Dynamic Digital Exhaust feature will be more dramatic if you use
Basic Programming